Contribution to the Genesis of Thermal Water of the North-east Perimeter of the Zenica-Sarajevo Basin, Bosnia and Herzegovina

The phenomena of thermal waters in the north-eastern periphery of the Zenica-Sarajevo Basin are caused by the geological structure, structural-tectonic and hydrogeological characteristics of the terrain. The genesis has not been fully addressed before. This paper presents the study of the genesis of thermal waters based on the geological structure, structural-tectonic and hydrogeological characteristics of the terrain, and the physiochemical and isotopic composition of water. The results provide a new contribution to the structure of this part of the Zenica-Sarajevo Basin and create a more realistic foundation for the future research of thermal water in this area.


Introduction
The thermal water springs of the north-eastern perimeter of the Zenica-Sarajevo Basin (Sidica, Tičići, Ribnica, Kraljeva Sutjeska, Toplik and Sedra) appear to be approximately linear from Zenica in the northwest, through Kakanj and Visoko, to Breza in the southeast (see Figure 1).
The genesis of thermal water of the north-east perimeter of the Zenica-Sarajevo Basin was not suffi ciently perceived and understood in the past. A small number of authors from the region studied this topic. Remarkable results were published by Josipović (1971), Đerković (1971), Miošić (1981), Miošić (1982), Slišković (1987

), Skopljak, (2006) and Skopljak & Vlahović (2011).
In his Mineral, Thermal, and Thermo-mineral Waters on the territory of Bosnia and Herzegovina, Josipović (1971) states that thermal water in the area of Kakanj is mildly hypothermic, with a temperature of 24-32°C, a normal pH value, and a mineralization value of 0.5-1.5 g/l, and it contains dissolved hydrocarbon, sulfate, calcium, and rarely magnesium and sodium ions. Josipović stated that the phenomenon of thermal waters in Kraljeva Sutjeska is outside the Sarajevo-Zenica tertiary Basin, located on its north-eastern edge (Josipović, 1971). While describing the thermal water in the vicinity of Kakanj, he states the following: "Thermo-mineral waters occur on the perimeter of the basin (Ribnica, Radići and Tičići) on the border of Oligo-Miocene sediments and limestones of the Upper Cretaceous. These waters are likely of primary accumulation origins. Thermal water in Ribnica is low in mineralization as a result of interference of river water and thermal mineral water in the area right next to the source" (Josipović, 1971). The sedimentary origin of these waters casts a shadow of a doubt on the similarities between ion interaction with the thermal waters in the area of the Kraljeva Sutjeska, and, to some extent, with thermal mineral waters of Ilidza, near Sarajevo. Josipović does not exclude the possibility that these spring waters are of similar origin.
In his paper on the Results of Previous Studies on Mineral, Thermal, and Thermo-Mineral Waters of Central Bosnia, Đerković (1971) provides a description of thermal waters at Sedra in Breza, Ribnica, Tičići and Kraljeva Sutjeska near Kakanj. Regarding the genesis, Đerković (1971) stated that thermal water is generated by the infi ltration of atmospheric water that sinks, is heated and then re-emerges on the surface. For thermal water at Ribnica, he believes that the water re-emerges at the north-south fault, from the limestone and coarsegrained brecciated limestone and sandstone.
In his work on Genetic Categorization of Mineral, Thermal and Thermo-Mineral Waters of Bosnia and Herzegovina, Miošić (1982) incorporates thermal waters of the north-east perimeter of the Zenica-Sarajevo Basin into a hydrogeological structure of the "artesian basin and inter-mountain depressions", describing the zone of the Sarajevo-Zenica depression. Regarding the The Mining-Geology-Petroleum Engineering Bulletin and the authors ©, 2017, pp. 17-30, DOI: 10.17794/rgn.2017.4.2 genesis of thermal waters in this area, Miošić (1982) states the following: "The primary gas composition at Ribnica, Kraljeva Sutjeska and Sedra is changed by the infi ltrating atmospheric gases, as is shown by the changes in gas composition. While Radići and Tičići have a signifi cant content of CO 2 , Sedra and Kraljeva Sutjeska have a 10 times smaller amount of gases. The deposition of ferrous compounds and traventine in Sedra and Kraljeva Sutjeska implies the reducing conditions that prevail in the primary reservoir. According to Josipović (1971), the silicifi ed cavities in limestone confi rm the assumption of intense hydrothermal processes in the Tertiary, which indicate that the "thermal waters are partly the remains of those events in Kraljeva Sutjeska (Miošić, 1982). Miošić also claims that the water is predominantly of atmospheric origin and that their current accumulation does not originate from hydrthermal conditions. Fault tectonics cause the ascension of water that is being heated by fast convection of the primary aquifer that is in the deeper horizons (Miošić, 1982).
In his paper on the Hydrogeological and Hydrothermal Characteristics of Thermo-mineral Waters at Ribnica and Tičići near Kakanj, Slišković (1987) claims the following: "The accumulation of thermal water in Rib-nica and Tičići near Kakanj is formed in the fl oor of Oligo-Miocene sediments and Jurassic-Cretaceous fl ysch at the depth of 1500-2500 m below the ground surface in carbonate environments. Hot water circulates to the surface of the terrain though young (neotectonic) faults, to a depth of about 400-600 m where it mixes with the descendent underground streams of cold water until they erupt at the earth's surface along the faults." The upward movement of thermal mineral water ends in Upper-Cretaceous, partly brecciated and fl ysch-like limestones (calcarenites), that represent the primary and secondary groundwater aquifer. The primary aquifer is in the southern zone under the thick layers of the Oligo-Miocene Sarajevo-Zenica Basin. The secondary aquifer is on the northern edge of the pool towards the Jurassic-Cretaceous fl ysch. The entire Oligo-Miocene and Miocene sediments represent an overburden insulator for the thermal waters which are formed in the Cretaceous limestones. Based on the geological and hydrogeological developed model, he concludes the possibility of the formation of the primary aquifer thermal waters even in the Anisian T 2 1 limestones, which are located in the area of Kakanj, most probably at depths of 1500 to 2500 m ".
Skopljak, (2006) in the work "Groundwater interrelations of Ilidza near Sarajevo" and Skopljak & Vla-  Sarajevo, Bosnia and Herzegovina," show that mineral water southwest periphery of the Zenica-Sarajevo Basin primarily have the genesis of evaporites permian sediments.
Based on earlier studies of the genesis of thermal waters of the north-east perimeter of the Zenica-Sarajevo Basin, it can be concluded that the inquiry of the genesis of thermal water in this area had not been fully resolved, and that the answers should continue to be searched for through hydrogeological and hydrochemical investigations and trials.
The aim of this paper is to give a contribution to understanding the genesis of thermal waters north-east periphery of the Zenica-Sarajevo Basin on the basis of geological, structural-tectonic and hydrogeological characteristics of the terrain, and hydrogeochemical research conducted in the wider area.
To solve hydrogeological unknowns, hydrogeochemical methods were used, which included defi ning the hydrochemical type of water, the correlation of the main components in the water, genetic classifi cation calculation of ion relations and mixing diagrams. As a complement to the knowledge obtained, hydrogeochemical methods in determining the genesis of thermal water was used as well as isotopic composition of thermal water at the site Tičići based on correlation isotope δ18O and δ2H (Craig, 1961).

Study area
Thermal waters of the north-eastern perimeter of the Zenica-Sarajevo Basin spring in the extreme southwestern slopes of the Ravan and Zvijezda mountains, in the area that gradually transforms into the valley of the Zenica-Sarajevo Basin and the valley of Bosnia. This terrain is characterized by large differences in altitudes, from approximately 450 m a.s.l. in the valley of Bosnia to 1300 m a.s.l. at the mountain peaks.
The largest and most important waterways in the north-eastern periphery of the Zenica-Sarajevo Basin are: the rivers Bosnia, Stavnja, Goruša, Trstionica, Zgošća and Ribnica. The area located on the north-eastern perimeter of the Zenica-Sarajevo Basin is characterized by a moderate continental climate. The average annual precipitation is about 975 l/m 2 and the average annual temperature is 11.2°C. Thermal water springs (Sidica, Tičići, Ribnica, Kraljeva Sutjeska, Toplik i Sedra (see Table 1) have been located in the north-eastern periphery of the Zenica-Sarajevo Basin.

Geological setting
Thermal waters are located in the north-eastern periphery of the Zenica-Sarajevo Basin. According to the geotectonic zoning by Hrvatović (2006), three distinct tectonic zones can be identifi ed: 1) Non-native Paleo-zoic and Triassic formations (Mid-Bosnian Schist Mountains) built mainly of Paleozoic formations; 2) Bosnian fl ysch which represents the clastic-carbonate formation of Jurassic-Cretaceous and Upper Cretaceous fl ysch deposits and 3) Post-orogenic Neogene and Quaternary sediments with limnic deposits and Zenica-Sarajevo Basin coal (see Figure 2). Šarić (2015) shows the position of the thermal water sources in relation to the tectonic units that are closely related to the terms of their appearance, or genesis (see Figure 3).

Geological Structure
The geological structure of the fi eld of research to the basic geological map (Pamic, et al 1978) participate rocks Paleozoic, Mesozoic and Cenozoic (see Figure 4). Paleozoic rocks are made of Silurian-Devonian (S, D and Upper Permian (P 3 ) metamorphites. Silurian-Devonian deposits are represented by quartz-sericite schists. Upper Permian deposits are represented by conglomerates, sandstones, shales, and most likely, as in other parts of the Mid-Bosnian Schist Mountains, marly limestone with layers and lenses of gypsum. Deposits of Upper Permian lay transgressively through the Silurian-Devonian formations. The thickness of the gypsum layer is in the range between 30-40 m.
Mesozoic sediments are mainly represented by the sediments of Jurassic-Cretaceous and upper Cretaceous fl ysch and Triassic limestones (Hajdarević, 2012). Middle Triassic sediments are found in the south-western rim of the basin. These sediments are about 200 m thick massive dolomites, dolomitic limestones, limestone  The Cenozoic sediments are represented by Oligo-Miocene, Miocene, and Quaternary deposits (Andric et.al, 2015). Within the Oligo-Miocene polyfacies complex (Ol, M), there are three distinct units: 1) the basal zone, 2) the travertine limestone zone, 3) and the colored zone. The total thickness of this complex is about 600-700 m. The sediments of the basal zone are represented by sandstones, conglomerates, and ferreous oolitic limestones, marls and clays. Travertine limestones are lumpy and oolitic, and are conglomeratic or brecciated at the base. The sediments of the colorful zone are mainly composed of conglomerates that alternate with sandstones, marls and clays.
Miocene sediments are lacustrine sediments of the Lower-Middle (M 1,2 ), Intermediate (M 2 ) and Middle-Upper Miocene (M 2,3 ). The sediments of the Lower-Middle Miocene are represented by the main coal zone consisting of marls, sandstones, conglomerates and clays with major and an Orascom carbon layer. The thickness of this zone is about 150 m. The sediments of the Middle Miocene are represented by roof coal limestone zone with roof coal seams ( 1 M 2 ), with a total thickness of about 70 m, and the transition zone ( 2 M 2 ) with thinly layered marls and sandstones with a thickness of 350-450 m (Muftić,1965). Middle-Late Miocene (M 2,3 ) is represented the Lasva series of conglomerates, sandstones, marls and rarely limestones. The total thickness is about 400 to 800 m (Milojević, 1964). Quaternary formations have a greater distribution in the valley of the river Bosnia, and at the mouths of its tributaries. In this region, Quaternary is represented by alluvium (al) composed of gravel of various degrees of grit, with frequent sands and clays.

Tectonics
The tectonics of the terrain were analyzed by using the structural forms downloaded from the available Basic geological map sheet Vares (Pamic et al 1978) and Hrvatović (2006) paper on the geotectonic zoning. Two main nappes dominate this area: 1) the Bosnian fl ysch Nappe and 2) the Durmitor Nappe.
The Bosnian fl ysch Nappe consists mainly of fl ysch formations deposited from Liassic to the Paleogene. This nappe is largely thrusted on the Raduški Nappe and the tectonic block of the Mid-Bosnian Schist Mountains. In the thermal water zone, the Bosnian fl ysch Nappe is made of Jurassic-Cretaceous and Upper Cretaceous fl y-sch sediments, drawn on the Triassic and Paleozoic sediments. The Durmitor Nappe is made of predominantly Triassic carbonate rocks and Paleozoic formations of south-eastern Bosnia. It covers a wide area of Vares in the north-west to Foca and Cajnice in the south-east. The Durmitor Nappe is largely thrusted on the Bosnian fl ysch Nappe. In Vares, the Ophiolite Nappe is thrusted over the Durmitor Nappe, while in the south-east, in the area of Romanija and Devetak, the Golijska Nappe is partially thrusted over the Durmitor Nappe.
On the geological cross-section (Hrvatović, 2006) between Sarajevo and Vares, a thick Bosnian fl ysch Nappe is thrusted over the non-native Palaeozoic-Triassic formation in the south-west (see Figure 5). In the north-east, the Triassic formations are thrusted on top of the Bosnian fl ysch at the forefront of the Durmitor Nappe. The basement of the Bosnian fl ysch is most likely composed of Triassic sediments, while limnic deposits with coal were deposited over fl ysch in the Zenica-Sarajevo Basin.

Hydrogeological setting
The area of research and thermal water became part of hydrogeological fi eld "Bosnian fl ysch" and periphery hydrogeological fi eld "Post-orogene neogene formacije" or periphery Zenica-Sarajevo Basin . In the thermal waters zone of the north-east perimeter of the Zenica-Sarajevo Basin, there are two basic hydrogeological rock characteristics: • Permeable rocks • Impermeable rocks

Permeable Rocks
• permeable rocks with intergranular porosity • permeable rocks with intergranular and/or fracture porosity • permeable rocks with fracture porosity • permeable rocks with cavernous-fracture porosity. Permeable rocks with intergranular porosity are alluvial and terraced layers (al, t 1 , t 2 ). Hydrogeological parameters, on average, have the following values: T = 15-50 m 2 /day; q = 0.1-0.3 l/s/m and Q max = 0.5-2.0 l/s (Geological Survey of Sarajevo, 1988). Drinking water aquifers were formed in these layers in the expanded river valleys. The underground water reserves in these aquifers are limited due to the small distribution and thickness of the alluvial deposits, and are also limited by fl uctuations in the fl ow and water levels of the rivers that feed them.
Permeable rocks with intergranular and/or fracture porosity are the deposits of the "Lasva series" (M 2,3 ). Hydrogeological parameters, on average, have the following values: T = 15-30 m 2 /day. Limited quantities of ordinary water appear in these rocks, partly under pressure, which are discharged at the springs, mainly with small yields (Qmax = 0.5-2.0 l/s).
Permeable rocks with fracture porosity are separated into three classes: High permeable rocks with fracture porosity are found in the Upper Cretaceous deposits (K 2 2,3 ). The transmissibility of this formation is different depending on the representation of the individual members; weak in shale and marl facies, and good in limestone and brecciated limestones facies. Hydrogeological parameters, on average, have the following values: T = 50-100 m 2 /day; Qmin = 0.5-5.0 l/s (Geological Survey of Sarajevo, 1988). These rocks have a hydrogeological function of ordinary cold water aquifers and secondary aquifers of the thermal waters in the north-eastern periphery of the Zenica-Sarajevo Basin. Medium-permeable rocks with fracture porosity are found in the lower Oligo-Miocene ( 1,2 Ol, M, 2 Ol, M). The transmissibility of these deposits is relatively poor to good, and hydrogeological parameters, on average, have the following values: T = 15-50 m 2 /day; Qmin = 0.05-5.0 l/s. Limited quantities of ordinary water are found in these rocks, partly under pressure, which are discharged at the springs, mainly with very small yields (Q <1.0 l/s). Low Permeable rocks with cavernous-fracture porosity are represented in the Middle Triassic (T 2 ) sediments. Transmissibility of these deposits is mainly good and hydrogeological parameters are, on average, T = 15-300 m 2 /day (Geological Survey of Sarajevo, 1988). These rocks have the hydrogeological features of ordinary cold water aquifers in Vares and thermal water aquifers in the north-eastern periphery of the Zenica-Sarajevo Basin.

Impermeable Rocks
Mostly impermeable rocks are classifi ed into two groups: • mostly impermeable complexes • practically impermeable rocks. Mostly impermeable complexes are represented by clastic Jurassic-Cretaceous (J, K) and Upper Cretaceous fl ysch (K 2 1,2 ), higher levels of Oligo-Miocene ( 1 Ol, M, 3 Ol, M), Lower-Middle Miocene (M 1,2 ), the transition zone of the Middle Miocene ( 2 M 2 ) and the Upper Miocene ( 1 M 3 ). Water permeability in these rocks is very poor so that they do not form aquifers. The transmissibility of these deposits is very low T≤15 m 2 /day, and the yield of the spring appears to be very small Q ≤ 0.05 l/s. Practically impermeable rocks are Silurian-Devonian in age (S, D). These are the deposits without an aquifer with no transmissivity and springs that do not appear at the surface.

Materials and methodology
The genesis of thermal waters in the north-eastern periphery of the Zenica-Sarajevo Basin is determined by analysis of the geological structure, tectonic relations and the hydrogeological characteristics of the terrain, and analysis of hydrogeochemical indicators and the isotopic composition of water.
We analyzed the sources "Sidica", "Tičići", "Ribnica", "Kraljeva Sutjeska", "Toplik" and "Sedra", which were used in laboratory values obtained with hydrogeochemical and isotopic indicators of water. Geological structure, structural-tectonic and hydrogeological characteristics of the area of the thermal water were analyzed through geological and hydrogeological profi les.
Hydrogeochemistry methods included: 1) the defi nition hydrogeochemical water type, 2) the correlation of the main components, 3) the calculation of ionic relationships, 4) genetic classifi cation and 5) mixing diagrams. Hydrochemical water type is defi ned by Piper diagram (Piper, 1953). Genetic Code Sulinowo water was determined by the classifi cation (1948) based on the value of the relationship of the major ions: Na-Cl, Na-Cl-SO4-Na and Cl-Mg. The correlation of the main components is affected through the relationship of calcium and sulfate ions and mineralization and temperature. Diagram mixing was done for the sources Tičići and Rayon by the method of real (Bogomolov & Silin- Bekchurin, 1955). As a complement to the knowledge obtained, hydrogeochemical methods in determining the genesis of thermal water was used, and isotopic composition of thermal water at the site Tičići based on the correlation isotope δ 18 O and δ 2 H (Craig, 1961).

Discussion
The study of the genesis of thermal waters in this paper was carried out based on geological structure, structural-tectonic and hydrogeological characteristics of the terrain, and the physio-chemical and isotopic composition of water.

"Sidica" thermal water spring
Sidica Spring is located in the region of the identically-named village, 1 km south of Mošćanica, west of Ze-nica. The spring appears to be on the contact between Oligo-Miocene and Upper Cretaceous deposits (see Figure 6).
The spring is a fracture-type spring with the characteristics of entrance. The discharge of the spring is 0.2 l/s, the mineralization is 438 mg/l and the temperature is 17 o C. Chemically, the water is a hydrocarbonate-calcium-magnesia type.

"Tičići" thermal water spring
Tičići Spring represents the most signifi cant occurrence of thermal waters in the area of Kakanj, and beyond. At this site, the thermal water discharges in a form of a spring. The spring is of the knotted type and emerges to contact the Lower Miocene sediments (M 1 1 ) and limestones of the Upper Cretaceous (K 2 2,3 ) (see Figure  7). Two sources of thermal waters were identifi ed at this site; the fi rst spring is on the right side of the highway and discharges 2.5 l/s with a temperature of 24-27°C; the second spring parallel to the highway axis that discharges 0.5 l/s with a temperature of 22°C. The results of the spring water quality sampling indicate that the water is of the hydrocarbon-sulphate-calcium-sodic type with a mineralization of about 1000 mg/l (Miošić, 1977).
In 1985-1986, a drilling program was conducted at the Tičići Spring, with drilling boreholes IT-1 and IT-2 (Slišković, 1987) After drilling IT-1, a hydrological relationship between Banja Spring and Tičići Spring was established. Banja Spring had the discharge increased to 30 l/s with a temperature of approximately 50°C.
The exploration drilling of IT-1 was conducted in 1985. The depth of the drillhole was 300.5 m, with a final diameter of 101 mm. The basic parameters of the drillhole IT-1 showed a discharge of 30 l/s and a temperature of 54 ° C. The exploration drilling of IT-2 was conducted in 1986. The depth of the drillhole was 203 m. The drilling was carried out just above the Sarajevo-Zenica highway in the exact same geological environment as IT-1 that was 350 m away from IT-2. The fi nal hole diameter was 86 mm. The drilling program was terminated, and a concrete block was built over it. The basic characteristics of the drillholes showed a discharge of 22 l/s and a temperature of 39°C.

"Ribnica" thermal water spring
In the vicinity of the village Ribnica near Kakanj is a documented occurrence of a thermal water spring, which is now buried beneath the landfi ll Vrtlište (see Figure 7). According to the available data, the spring emerged at the contact between Oligo-Miocene sediments and the Upper Cretaceous limestones (Josipović, 1971).
A more detailed description by Đerković (1971), who worked on describing Ribnica, states the following: "This water emerges at a north-south fault from limestone fl ysch and grained brecciated limestones and sand-stones." (Đerković 1971). The source of this scatteredtype thermal water appeared about in the riverbed of Ribnica River. Its abundance was diffi cult to determine due to mixing with the Ribnica River, but is estimated at 10-30 l/s. The mineralization of water at the spring is 684 mg/l and the temperature is 28.9°C. Geochemically, the thermal water Ribnica is a hydrocarbonate-sulphatecalcium-magnesia type. After detailed hydrogeological research at this site, two drillholes RB-1 (see Figure 7). and RB-2 were explored, which indicated about 100 l/s of thermal water (Slišković, 1987) The well RB-1, at a depth of 40 m, had an optimum discharge of 40 l/s and a temperature of 28°C. The well RB-2, at a depth of 180 meters, had an optimum discharge of 80 l/s and a temperature of 30°C with the pressure of 0.04 bar at the mouth of the well.

"Kraljeva Sutjeska" thermal water spring
The thermal water spring at Kraljeva Sutjeska is located just above the mouth of the stream Bukovac in the Trstionica River. Thermal waters appear at the contact of the cracked and karstifi ed limestone of Upper Cretaceous (see Figure 8). The spring of the thermal water is of the knotted type.
The mineralization of water at the source is 691.66 mg/l with a temperature of 21°C. Given that the source was capped and redistributed to the water supply system, it is not possible to measure the discharge. According to Josipović (1971), the discharge of the main spring is around 25 l/s. Geochemically, the thermal waters are of hydrocarbonate-sulphate-calcium-magnesia type.

"Toplik" thermal water spring
The thermal water spring Toplik is located in Podvinjci, north-east of Visoko. The spring emerges at the contact of Oligo-Miocene and Upper Cretaceous deposits (see Figure 9). The thermal water spring is of the knotted type. The mineralization of water is 550.81 mg/l

"Sedra" thermal water spring
The thermal water spring Sedra is located about 2 km from Breza, on the left side of the river Stavnja, below the Breza-Vares road. The spring is of the scattered type and emerges from the Cretaceous fl ysch sediments close to the Tertiary sediments (see Figure 10). The mineralization of water was 1121 mg/l, with a temperature of 19.3°C. The source Sedra, according to Đerković (1982), has an overall yield of about 32 l/s. Genetic types of the thermal waters of the north-east perimeter of the Zenica-Sarajevo Basin were determined by using Sulin's diagram, based on the value of the relationship of the main ions: Na/Cl, Na-Cl/SO 4 , and Cl-Na/ Mg. The diagram shows that all the analyzed thermal waters in this area have Na-Cl/SO 4 <1, that is, they are of the sulphate-sodic type and originate from a terrestrial environment (see Figure 11).
The study of the genesis of Tičići thermal water was done based on the isotopic composition of water by employing deuterium ( 2 H) and oxygen 18 ( 18 O) (Pezdić, 1985). The content of deuterium in Tičići thermal water near Kakanj ranges from -80.0% δ 2 H to -80.10% δ 2 H, and oxygen from -11.16% δ 2 O to -11.17% δ 2 H (see Table 2). These isotopic values indicate the atmospheric origin of the thermal water (see Figure 12), because the content of 18 O and 2 H of thermal water and precipitation lay in the so-called middle right, reproduced by the equation H = (8xδ18O) + 10. From the diagram, we conclude that the thermal waters in Tičići were created in the Pleistocene, during the period of cold climate. In the future, it is necessary to do isotopic tests on all thermal springs in the north-eastern perimeter of the Zenica-Sarajevo Basin in order to defi ne their genesis and regularity of appearance.
The testing of thermal and cold waters in this area was performed by the analysis of their mixtures, the correlation of the chemical composition and temperature, as well as the relationships between sulphate, chloride and calcium in the groundwater. Testing of the mixing of thermal water is of great importance for determining their relationship with drinking water.
The diagram of thermal water mixture in the northeastern part of the Zenica-Sarajevo Basin shows that the thermal waters have a mixed origin (see Figures 13  and 14).
Water mixing most likely occurs in the area of Upper Cretaceous sediments, between a cold (drinking) water from the karst aquifers formed in the limestones of the Upper Cretaceous, and thermal waters, most likely with much higher temperatures that originate from the Triassic sediments, which are in contact with the Upper-Permian evaporites. Water mixing occurs at great depths without the infl uence of the daily climate fl uctuations and other factors.
The further evidence for water mixing comes from Tičići from the borehole IT-1 at a depth of 300.5 m. The thermal water temperature at depth was 54°C, while the temperature at the spring located in the immediate vicin-ity of the well was 26°C. As was demonstrated, the thermal waters of the north-eastern perimeter of the Zenica-Sarajevo Basin have a relationship with the Upper Permian sediments containing gypsum and anhydrite (evaporates).
The Upper Permian sediments with gypsum were found at the site Kondžilo, Javorci and Prževine in the south-western part of the Zenica-Sarajevo Basin, so that they are to be expected in its north-eastern perimeter, as well, a hypothesis that is supported by the study of the genesis of thermal waters in this area. In the future, it is necessary to perform a broader chemical analysis of all thermal springs in the north-eastern perimeter of the Zenica-Sarajevo Basin in order to defi ne their genesis, regularity of occurrence and mixing. The relationship of thermal waters and evaporates was determined by using sulfate and calcium, as is shown in the diagram (see Figure 15).
The calcium (Ca) and sulfate ion (SO 4 ) from the thermal waters of the Zenica-Sarajevo Basin mainly originated from the dissolution of gypsum shown in the reaction: CaSO 4 x 2H 2 O à Ca + SO 4 + 2 H 2 O. The average value of the Ca/SO 4 is 2-3, corresponding to the interpretation of gypsum dissolution. Diagonal lines in Figure  15, and the values indicate a negative deviation of the evaporite line (Ca/SO 4 = 2-3).
The ratio Ca/SO 4 indicates that the thermal waters in this area are a result of a mix of two types of water; each circulating through the Upper Permian deposits containing gypsum and other waters originating from the limestones. Schoeller's diagram of the thermal waters of the study area (see Figure 16) shows that all the thermal waters have a very similar ionic composition, which also implies similar conditions of origin, accumulation, fl ow and discharge. The thermal waters have different mineralization and temperatures (see Figure 17). The highest mineralization comes from the water spring Sedra, and the highest temperature comes from the Tičići Spring. There is an increase of temperature with increasing mineralization at almost all springs, except at the Sedra spring. Higher mineralization and lower temperatures of the Sedra thermal water spring can be explained by a lower depth of burial of the Upper Permian deposits in this area.
The Piper plot shows that all the thermal waters of the north-east perimeter of the Zenica-Sarajevo Basin are of the same hydrochemical type or sulphate-hydrocarbonate-calcium type (see Figure 18). The formation of the above hydrochemical type of thermal waters in this region is directly dependent on the chemical composition of the rocks through which they fl ow. An increased concentration of sulfate in all thermal waters indicates their fl ow through, and probably the formation within the Permian sediments with lenses of gypsum and anhydrite.

Conclusion
Taking into account the results of isotopic analyses, the geological structure, structural and hydrogeological characteristics of the studied area, the genesis of thermal waters of the north-east perimeter of the Zenica-Sarajevo Basin is as follows: • All occurrences of thermal water have a similar genesis • Thermal waters are of atmospheric origin • Thermal waters are of sulfate-sodic type • Thermal waters originate from a terrestrial environment • Thermal water accumulates in the basement of Jurassic-Cretaceous fl ysch • Thermal waters emerge to the surface through fault zones • Thermal waters are mixed with cold water at greater depths shielded of the daily temperature fl uctuations and other factors • Thermal waters have different mineralizations and temperatures • Thermal waters have had almost identical conditions of origin, fl ow and discharge. The results of this research contribute to explaining the genesis of the thermal waters of the north-eastern perimeter of the Zenica-Sarajevo Basin, their mineralization, chemistry and temperature. Also, this data con-tributes to new considerations of geological structure of this part of the Zenica-Sarajevo Basin and its rim, as well as creating a more realistic foundation for the future research of thermal waters in this area. The confi rmation of these results for the study of the genesis of thermal waters in the north-eastern periphery of the Zenica-Sarajevo Basin can be obtained by performing large scale isotopic tests on all springs and wells, which is planned to take place in the next phase of the research.